Reconditioning files



Patented Nov. 24, 1942 RECONDITIONING FILES Simon M. Cleja and John W.Hladky, New York, N. Y., assignors to Trans-American DevelopmentCorporation, New York, N. Y., a corporation of New York I No Drawing.Application May 29, 1942, Serial No. 445,101

2 Claims. (Cl. iii-24) The invention relates to an improved process ofchemically reconditioning used and worn steel files and like tools; theprimary object of the invention being to reduce the time required torecondition the files and the like while substantially eliminatingliability of the reconditionedfile's to either immediate and eventualdeterioration or loss of durability growing out of the processingthereof.

Other important objects and advantages of the invention will be apparentfrom the following description wherein a preferred embodiment of theinvention is set forth for illustration.

It is generally conceded that a satisfactory reconditioning of used andworn steel files can be achieved only through efficient performance ofthe following steps and operations:

(1) Cleaning, comprising (a) removal of organic and loosely adheringforeign matter, and (b) removal of iron oxide or rust and scale;

(2) Etching to resharpen the teeth or cutting edges; and

(3) Finishing, comprising (a) restoration of the original metallic graycolor, (b) stabilization of the restored color, and (c) drying of thefiles .after treatment.

Although some of the prior art processes fulfill in one degree oranother the above stated requirements, none of the prior processes ofchemically reconditioning used and worn files are suitable for orcapable of industrial applicationon a large scale whereby a large numberof files can be satisfactorily resharpened in a working day.

The present invention overcomes the foregoing objection to presentprocesses as Well as other to remove all loosely adhering foreign matterfrom them by immersing the files-in a boiling bath consisting of causticsoda solution prepared by dissolving from 50 to 100 grams of causticSoda inl kilogram of water.

H. The files are then removed from the caustic soda solution and sprayedwith water at a pres-- sure of about 200 pounds per square inch. Theimpact and washing action of the water at this pressure cleans the filesthoroughly all over and removes all loose foreign matter not removed bythe caustic soda bath. a

III. The files are placed in a bath consisting of about 165 grams ofcommercial hydrochloric acid (21 Be.) in ab'o'ut 1000 c.c. of Water, toremove the iron oxide which is not removed from the files by the causticsoda bath and the pressure washing. It is to be noted thatjfilesprocessed by steps I and II do not require long immersion in thehydrochloric acid solution, two or three hours being ample to remove theiron oxide and prepare the files for the next step.

IV. The files are washed all over with water sprayed at a pressure ofabout 200 pounds per important objections by making possible thefollowing advances over the prior art:

(1) Resharpening of a large number of files in one working day.

(2) Obtain sharp and uniformly shaped teeth.

(3) The original durability of the files is unaffected.

(4) Very substantial reduction in the amount of time and labor requiredfor the reconditioning.

(5) Elimination of the use of brushes or rinsing by substituting highpressure water spray for the usual brushing and rinsing operationsprescribed by prior processes.

(6) Elimination of the necessity of greasing the reconditioned filesthrough permanent restoration of the original gray metallic color of thefiles.

The steps and operations constituting the present invention are asfollows:

I. The files to be reconditioned are degreased square inch. This removesall traces of hydrochloric acid and leaves a chemically clean metallicsurface, ready for etching.

V. The files are immersed in an etching bath consisting of a 12% nitricacid solution, prepared by mixing 18 parts weight of commercial nitric-.a'cid (42 B.) and 82 parts by Weight of water.

The files are usually kept in this solution for from. five to sixminutes, but the time can be extended. for a fraction of a minutelonger, in the case of extremely worn files which require more etchingthan less worn files, although too long residence in the nitric acidbath is damaging to the file teeth. The temperature of the nitric acidbath during etching should not be permitted to go higher than 50 C. Thefiles may or may not'be removed and reimmersed in the bath during theetching. It will be recognized that the nitric acid etching reduces thefiat tops of worn file teeth and restores their cutting edges.

VI. The etched files are sprayed all over with water at a pressure ofabout 200 pounds per square inch to wash them free of nitric acid and toarrest the etching action.

VII. The etching darkens the surface color of the files, and the naturalmetallic gray color of the files is restored by immersing the files forfrom ten to twenty minutes in a hydrochloric acid solution consisting of340 grams of commercial hydrochloric acid (21 Be.) and 1000 c. c. ofWater, in a ratio by weight of about 9 parts of acid to 1 part of water.

VIII. In order to prevent the rusting which normally follows quicklyafter the acid treatment, due to the catalytic efiect of traces of acidremaining on the surface of the files, the files are sprayed with waterat 'a pressure of about 200 pounds per square inch to remove all suchtraces of acid.

IX. To rust-proof the files and fix the metallic gray color of thefiles, the files are immersed in a sodium silicate solution, preparedbymixing 1 part by volume of commercial sodium silicate (40 B.) with from3 to 5 parts by'volume of water.

X. The files having been removed "fromthe sodium silicate are dried bysuspending them freely in the air. The drying may be s'peededup bysuspending the files in an air current produced by a blower or exhaustfan.

Although there is set forth and described herein a preferred embodimentof the invention, it lsnot desired to limit the application of theinvention thereto, beyond the scope of the subjoined claims.

Having described the invention, what is claimed as new is:

1. In a time and cost reducing process of chemically resharpening usedand worn files, said process involving immersion of the files in ahydrochloric acid bath for about 2 to 3 hours to remove and loosenforeign matter from the surface preparatory to etching with nitric acid,the step of spraying the files'with water at a pressure of about 200pounds per square inch after removal from the hydrochloric acid bath, toremove remaining surface matter and traces of acid, then immersing thefiles in the nitric acid bath for a relatively short period of time,thereby restoring the sharpness of the file teeth, then washing theetched files and removing traces of nitric acid therefrom by sprayingthem with water at a pressure of about 200 pounds per square inch inorsquare inch to prevent immediate rusting of the files, thenrust-proofing the files and stabilizing the natural gray metallic colorthereof by immersing the washed files in a sodium silicate solution ofabout 1 part of sodium silicate in 3 to 5 parts of water, by volume,then removing the files therefrom and drying the files in the air.

2. In a quick-acting process of chemically resharpening files,consisting in first removing all foreign matter from the files by ashort time immersion in a hot bath solution of from 50 to 100 grams ofcaustic soda in 1 kilogram of water; second removing the files from saidbath and spraying them with water at a pressure of about 200 pounds persquare inch; third placing the thus cleaned files in a second bath for 2to 3 hours containing a solution of about 165 grams of commercialhydrochloric acid (21 B.) in about 1000 c. c. of water thus removing anypossibly adhering iron oxide; fourth after removing the files from thebath subjecting them to a water spray of 200 pounds per square inchpressure in order to obtain a chemically clean metallic surface; fifthimmersing the files during 5 to 7 minutes in an etching bath consistingof a 12% nitric acid solution containing a mixture of about 18 parts byweight of commercial nitric acid (42 B.) and '82 parts of water and at amaximum temperature of 50 0., thereby restoring the cutting edges of thefiles; sixth again spraying the files with water at a pressure of about200 pounds per square inch in order to arrest the etching action;seventh immersing the thus cleaned files for 10 to 20 minutes in asolution consisting of about 340 grams of commercial hydrochloric acid(21 B.) and 1000 c. c. of water at a ratio by weight of 9 parts of saidacid to 1 part of water, thereby restoring the natural gray color of thefiles; eight again spraying the files with water at a pressure of about200 pounds per square inch in order 'to remove all traces of acid; ninthimmersing the files in a solution of about 1 part by volume ofcommercial sodium silicate (40 B.) mixed with between 3 and 5 parts byvolume of water,

in order to rust-proof the files and fix the gray color thereon; lastlyremoving the files from the bath and air-drying them preferably by freesuspension in artificial draughtl SIMON M. CLEJA. JOHN W. I-lL'ADKY.

